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the new panda cub at the national zoo got checked out by zoo staff and veterinarians for the first time today. News4's Derrick Ward reports (Published Tuesday, Aug. 27, 2013)

Updated at 2:27 AM PDT on Monday, Aug 26, 2013

The National Zoo said the second cub birthed by Mei Xiang, their giant panda, was malformed in utero and never alive.

Mei Xiang gave birth to a cub Friday afternoon after approximately two hours of labor and a second cub was born Saturday at 7:29 p.m., but it was stillborn.

Dr. Suzan Murray, head veterinarian at the National Zoo, said the second cub was malformed around the head and was never viable. Murray said the cub was missing part of its skull and brain, and had deformities with its eyes and jaw.

Murray described the stillbirth as “very rare.”

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She said zoo personnel were able to examine the first cub hands-on for the first time. “All signs are that we have a healthy cub and we’re excited about that,” Murray said.

While they won’t know the sex of the cub for another couple of weeks, they were able to take vital sign readings. The cub weighs 137 grams or 4.8 ounces, had good heart and lung sounds, and good signs for intestinal function.

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“Mei Xiang is doing very well and the cub is doing very well,” said Dr. Brandie Smith, senior curator at the National Zoo.”

Smith said panda observers did not see the birth of the second cub, but noticed Mei Xiang doing some abnormally long grooming of a cub and didn’t notice any movement. She said there were some very tense moments until they heard the first cub squealing, indicating the presence of the second cub.

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“It was a few minutes of pure terror,” said Smith. “It was minutes between the cub not moving and the realization it was a second cub.”

Both mother and cub are resting comfortably. Smith said Mei Xiang is behaving like a very good mother and they are very excited about watching the cub grow.

Pandas take two years between pregnancies so there will be plenty of time until zoo personnel will be on the lookout for the next panda addition.

After Friday's birth, zoo officials in Washington, D.C. reported, Mei immediately picked the cub up and started cradling it.

Mei Xiang had been on a 24-hour pregnancy watch since Aug. 7 when she began cradling her toys, licking her body and "nesting." She was artificially inseminated twice March 30 after failing to breed naturally with the zoo's male panda Tian Tian. Officials say Mei and the cub will be in isolation for the next few months.

It's not clear who will be the proud father: Mei was inseminated with previously frozen semen from both Tian Tian and Gao Gao, a panda at the San Diego Zoo.

Mei Xiang has given birth to two cubs in the past. A female cub, born last September, lived only six days. Her birth was a surprise; she had not shown up on any ultrasounds. An autopsy determined she may have been born prematurely. Mei Xiang's only surviving cub, Tai Shan, was born in 2005 and now lives in China.

According to an agreement with the Chinese government, the cub will stay at the National Zoo for four years and will then be sent to China.